1. Field of the Invention
This invention relates to resinous compositions, particularly coating compositions, and to coated substrates. More particularly, this invention relates to coating compositions containing polymeric polyols cured with an aminoplast and which are hard, durable and which have surprising flexibility.
2. Brief Description of the Prior Art
Coating compositions comprising hydroxyl-containing polymers in combination with an aminoplast curing agent are well known in the art. Usually these compositions are prepared with an approximate stoichiometric amount of aminoplast curing agent. For hard, durable coatings, the hydroxyl number of polymeric polyol is relatively high and relatively high amounts of aminoplast curing agent are used. However, these hard, durable coatings are very rigid having relatively poor flexibility, particularly poor low temperature flexibility. For flexible coatings, the prior art has suggested relatively low loadings of aminoplast (on a percentage by weight basis). However, coatings prepared with these low aminoplast loadings do not have outstanding durability, nor hardness. It has been found in the practice of the present invention that hard, durable coatings with a surprising degree of flexibility can be prepared by curing polymeric polyols having low cured glass transition temperatures and preferably having a low hydroxyl functionality (as determined by hydroxyl value) with a substantial stoichiometric excess of an aminoplast curative.